I look at some of these questions as philosophical-ish in nature (posing questions, but not with the intent on comparing with observed reality), but not entirely. The relation between biology and what it takes and what it means to have consciousness is in many ways philosophical in that biological measurements are externally available to objective observers while the conscious state is only available to the conscious state entity. Without something like direct-trans-brain-communication (telepathy), any knowledge you have is a secondary source (someone else). First person observations, on the other hand, might be considered more likely to be subjective.
On the other hand, scientific answers can provide constraints on some otherwise philosophical conjectures.
Vrbic said:
But for me, the being is connected to brain activity.
Most biologists would agree.
I am assuming here by being, you me one's conscious self.
Data supporting this would be of the nature of:
- correlations between second hand descriptions of one's conscious experience and measurements of brain activity
- manipulations of brain activity
- perhaps with brain injuries of various kinds
Vrbic said:
I agree, it would be difficult to teach the frog something
For a lab that worked with frog behavior, it probably would not be that difficult. Choosing the task would be important.
Vrbic said:
But for me, the being is connected to brain activity. If you have a brain without any electrick activity even without blood and oxygen it dies.
I am sure that there have been brains without electrical activity that have returned to being active and behaving (if people) largely the same. Not quickly finding references about it however.
Things like people in comas or people who are chilled down for some medical reason will probably loose all brain activity. They can, in some cases, return to normal functioning.
@Laroxe might know this stuff.
What all brain activity is, is another hidden question here. As recorded by most EKGs, it probably reflects activity in the cerebral cortex (the "thinking" part). There are lots of other brain parts, in distant brain regions a normal EKG might miss.
Normally, neurons are supposed to start dying soon after blood flow (and therefore oxygen supply) is cut off. This is due to the high metabolic needs (glucose and oxygen) of nervous system tissues.
However, as body temperature goes down, metabolism (and therefore the metabolic needs) demand drops until it asymptotes close to zero. Without greatly reduced metabolic demand, the requirement for supplying it is much less. So there are conditions where lack of blood flow and oxygen will not kill the brain, if not for too long.
Vrbic said:
I think consciousness is made by electric impulses, not by "mechanical" construction of the brain.
Both the electrical impulses AND the mechanical structure over which they interact are considered important in determining the manner in which the overall brain performs. It is the combined functioning of the active neurons in the brain, and how they interact together which together, determine how the brain behaves and controls behavior (external and internal).
The structure of the brain is important because when a neuron is active, its structural connections determine which other neurons it can excite or inhibit. This will then alter how the overall network behaves.
Vrbic said:
The consciousness is gone. Very interesting is to think about a mechanism which brings the brain back to life. But I think it is very complicated. But let it be I'm asking if we can say that frog borns again and starts a new life as a new frog or continues old one?
It is not conscious activity which maintains maintains the continuity of one's consciousness. Arguably, it could just be the ability to recall past memories and then spin a convincing story for yourself about your self history (your life).
You go unconscious when you go to sleep. You wake up and (think you) are "the same person". There will have been numerous small changes in your brain over night as synaptic strengths change or whatever, but largely you "are the same", as far as you can tell.
As long as you are not getting significant brain damage or metabolic changes in what your brain is doing this will probably be the case for more significant losses of consciousness.
This is like the
Ship of Theseus, question: how much (pieces of wood) of a (greek) boat can you change before it is no longer the same boat.
On the other hand, many insects start their lives as worm-like larvae (caterpillars, maggots, etc.).
After their larval life,
holometabolan insects (who undergo a complete metamorphisis) pupate and begin their metamorphosis into their adult form.
During the metamorphosis in the pupae, many of their neurons die and are replaced by new cells generated by neuroblasts. Some neurons get reused, but they may lose their larval connections to other neurons and make new one to adult neurons. Lots of structural changes in the nervous system because there is often a lot of structural changes (and new control issues) in the periphery (the non-nervous system), like new muscles, for new functions and controls, to be used in new behaviors (flying would be a good example).
I would expect these insects (if they have a consciousness) to think of themselves as different (if they had such high thoughts).
Vrbic said:
How is possible to recover the same impulses in the same way to create the same creature? And the second question. How is even possible to re-started the dead body? The frog is dead in the point of view of our definition. No pulse no brain activity? What do cause re-start?
Just because the frog may appear inert does not mean it is irreversibly dead. As long as the cells still have their integrity, there is a possibility they could be revived. I work for an eyebank now and am now well aware that their are several kinds of cells (with normally low metabolic demands (since they are not very active)) that can survive for 24 hours after a person's death and still be useful for transplanting into someone else.
More active cells will have less time. Brain cells perhaps the least, but if their metabolic rate can be reduced they will have more time.
If they have evolved for periods of inactivity (perhaps the brain cells of turtles hibernating under water), they could well have evolved mechanisms which trigger states of low metabolic requirement when appropriate.
While ignoring the differences in memory like declarative memory or muscle memory, there are different stages of memory which are considered to relate to how the memory is being stored.
Initially, a memory will be in short term memory, thought to be something like signals churning around in a nerve network somewhere. This is electrical in nature and can be disrupted be electrical shock (shutting down electrical activity and causing the loss of the memory.
Eventually, the memory goes into long term memory (there can be a bunch of intermediate stages) where the electrical activity produces biological changes in the active neurons (amount of neurotransmitter, strengthen connections between cells active at the same time, grow more branches to make more synapses). Memories at this stage are not eliminated by electrical shocks that shut down brain activity or by biochemical blockers. Making these changes is called consolidating the memory. Before consolidation is done, the formation of long term memories can be blocked by biochemical interference (like blocking protein production).
